This is a proposal to expand knowledge of the ontogeny of response selectivity for behaviorally relevant sounds in the mammalian central auditory system. Developmental studies of language acquisition in human neonates, and song acquisition in birds strongly suggest the presence of an innate neural "template" or "blueprint" that guides the development of neural substrates that serve to direct attention towards sounds that are of behavioral significance. These studies further suggest that an auditory system is not a "blank slate" prior to experience, but is instead biased to wire itself in a species-specific, adaptive fashion. Little is known, however, of the genetic contribution to the underlying neural substrates. One aim of the proposed studies is to determine the ontogeny of response selectivity for the echolocation pulse at the midbrain and cortical levels of the pallid bat auditory system. The development of response selectivity for the downward FM sweep of the echolocation pulse will be examined from the time juvenile bats first develop a representation of their full audible range, to the time they beginning using echolocation. To separate the contributions of genes and experience, these studies will be conducted in bats reared in a normal social and acousticenvironment, and bats deprived of experience with the echolocation pulse. A second aim examines response selectivity in normal adult bats to (1) determine the response selectivity for the echolocation pulse at two levels of the auditory system, (2) examine the mechanisms that underlie selectivity for various dimensions of the echolocation pulse, and (3) establish a reference for assessing the maturation of selectivity in developing bats. The pallid bat central auditory system exhibits an extreme degree of selectivity for the echolocation pulse, which provides clear physiological probes with which to measure the maturation process. In lieu of our current inability to study the ontogeny of the mechanisms underlying speech processing in humans, the proposed studies offer an opportunity to examine the development of response selectivity for frequency modulated, speech-like signals at two levels of a mammalian auditory system.